Three-dimensional semiconductor mounting has come to be indispensable to realization of further enhance density and capacity. The three-dimensional mounting technology is a semiconductor production technology in which semiconductor chips are each thinned and they are stacked to form a multilayer structure while interconnecting them by silicon through electrodes (through silicon via (TSV)). To realize this, it is necessary to thin the substrate formed with a semiconductor circuit by grinding the non-circuit-formation surface (also called the “back side”) thereof, and to form electrodes inclusive of the TSV on the back side. Conventionally, in performing the back side grinding of a silicon substrate, a protective tape is adhered to the surface opposite to the surface to be ground, thereby to prevent the wafer from breaking during grinding. However, the protective tape uses an organic resin film as a support base material, and is insufficient in strength and heat resistance though flexible, so that the tape is unsuited to formation of the TSV or formation of a wiring layer on the back side.
In view of this, there has been proposed a system in which a semiconductor substrate is bonded to a support such as silicon and glass through an adhesive layer and which sufficiently withstand the steps of back side grinding, formation of TSV, and formation of electrodes on the back side. In this case, important is the adhesion layer in bonding the substrate to the support. The adhesion layer is required to be able to bond the substrate to the support without leaving any gap therebetween, to have durability enough to withstand the later steps, and to enable the thin wafer to finally be released from the support easily. The adhesion layer will be referred to herein as a temporary adhesion layer (or temporary adhesive layer) since the wafer is finally released (delaminated) from the support.
Hitherto, as a known temporary adhesion layer and releasing method therefor, a technology has been proposed in which a heat-fusible hydrocarbon compound is used as an adhesive, and bonding and releasing are conducted in a heat-molten state (JP-A 2003-177528). Although the technology is simple because of controlling by only heating, however, the technology is applicable to a limited range, due to insufficient thermal stability at high temperatures above 200° C.
In addition, a technology in which a silicone pressure-sensitive adhesive is used for the temporary adhesive layer has been proposed (WO 2015/072418). In this technology, a substrate is bonded to a support by use of an addition-curable type silicone pressure-sensitive adhesive, and, at the time of delamination, the laminate is immersed in a chemical capable of dissolving or decomposing the silicone resin, to thereby separate the substrate from the support. Therefore, it takes a very long time to achieve delamination, and it is difficult to apply this technology to an actual production process.
On the other hand, there has also been proposed a technology in which an adhesive containing a light-absorbing substance is irradiated with high-intensity light to decompose an adhesive layer, thereby releasing the adhesive layer from the support (JP-A 2013-534721). In this method, there is a merit that the process time per substrate in separating the substrate from the support is shortened, but a metallic compound must be used for converting the irradiation light into heat, so that there is a risk of contamination of the substrate with metal.